The present invention relates to an improved racket and a method for manufacturing same, and more particularly relates to improvement in the head-to-handle weight balance construction of a fiber reinforced plastic racket by molding process and advantageously usable for tennis.
In general, handling and playing characteristics of any racket are mainly related to, and affected by the strength of a player, especially gripping force of the player, the total weight of the racket and the weight distribution of the racket. In addition, influences by these factors vary from player to player in accordance with personal preferences. Among the factors, the manner in which the weight is distributed has a very definite bearing on the accuracy attainable on a given stroke and on the power or force of that stroke. Further, the weight distribution, i.e. the head-to-handle weight balance, determines the maneuverability of the racket, i.e. the speed with which the racket may be brought into position for striking balls.
In tennis parlance, a "light" racket is one in which the center of gravity is relatively closer to the grip portion of the racket, while a "heavy" racket is one in which the center of gravity is relatively closer to the head portion of the racket. A "light" racket is the more maneuverable of the two, that is, it can be brought into position more quickly to make the stroke.
With recent general trend of tennis players towards the so-called "speedy tennis", there is an increasing demand for the "light" racket which, assures high maneuverability, i.e. quick stroking. In addition, as described already, the influence on the racket maneuverability by the weight distribution greatly varies from player to player. In order to meet thus varying personal preferences of the players, it is desirable that the weight distribution of rackets may be stepwise adjusted from lot to lot of the rackets.
In the conventional manufacturing of a fiber reinforced plastic racket, an elongated core made of a foamed resin is wholly, wrapped and covered by an elongated "prepreg" envelope made of numerous reinforcing fiber preimpregnated with a thermosetting resin to prepare an elongated rod which then is curved and set in position in a mold. The resin is then hardened by application of heat under pressure to obtain a fiber reinforced plastic racket. This molding process is well suited for the mass-production now in fashion in every field of the industry. However, such a mass-production type molding process affords very little possibility in adjusting the weight distribution of the rackets in the above-described sense.
Thus, adjustment of the racket weight distribution is conventionally and generally dependent upon personal efforts of players using the racket. In one instance, a tape or tapes are wound around the grip portion of the racket in order to obtain firm grip on the racket. Although this measure may be effective in adjustment of the "grip" on the racket, it cannot sufficiently adjust the weight distribution of the racket due to the relatively light nature of the tape. Tape winding suited for ideal grip on racket by a player does not always bring about ideal weight distrubution suited for the personal preference of the player. Likewise, tape winding suited for ideal weight distribution for a player does not always assure ideal grip on racket by the player.
In the other instance, a sharp, weighted, metallic plug is inserted into the core of the racket grip portion from the butt end, thereby displacing the center of gravity of the racket towards the grip portion. Although this plug may adjust the weight distribution, i.e. the head-to-handle balance, of the racket, forced insertion of the plug into the foamed resin core tends to develop undesirable cracks in the core. In addition, long use of the racket having such a plug may cause shearing destruction of the foamed resin configuration embracing the inserted plug due to the bending stress and impact loading repeatedly acting on the racket. Such configurational destruction of the foamed resin core leads to loosening in support for the plug and generation of noises jar upon the ear at striking balls.